1. Technical Field
The present invention relates to a piezoelectric element, a piezoelectric actuator, a droplet-ejecting head, a droplet-ejecting apparatus, and a method for manufacturing a piezoelectric element.
2. Related Art
It is known that piezoelectric actuators or ink jet recording heads can be manufactured by thin-film technology to reduce the thickness of a piezoelectric element, allowing high-speed driving. For example, Japanese Unexamined Patent Application Publication No. 2000-326503 discloses an ink jet recording head that can be manufactured by thin-film technology.
In the ink jet recording head according to Japanese Unexamined Patent Application Publication No. 2000-326503, the top surface and the side surfaces of a lower electrode of a piezoelectric element are covered with a piezoelectric layer. Because the lower electrode is exposed to an oxidizing atmosphere in the formation of the piezoelectric layer, the lower electrode is formed of a noble metal, such as platinum, which is more resistant to oxidation than base metals.
Use of a lower electrode formed of an easily oxidizable base metal material may result in the oxidation of the lower electrode in the formation of the piezoelectric layer, causing an increase in the volume of the lower electrode. This expansion may result in the detachment of the lower electrode or the occurrence of cracks. Thus, the lower electrode has a low degree of freedom with respect to the selection of the electrode material.